text: Acetylides of the type RCM are widely used in alkynylations in organic chemistry.  They are nucleophiles that add to a variety of electrophilic and unsaturated substrates. A classic application is the Favorskii reaction.
  Illustrative is the sequence shown below, ethyl propiolate is deprotonated by n-butyllithium to give the corresponding acetylide.  This acetylide adds to the carbonyl center of cyclopentanone. Hydrolytic workup liberate the alkynyl alcohol.